U.S. patent number 6,281,397 [Application Number 09/235,378] was granted by the patent office on 2001-08-28 for catalytic composition for the hydrogenation of olefinically unsaturated organic compounds.
This patent grant is currently assigned to Enichem S.p.A.. Invention is credited to Gianfranco Longhini, Francesco Masi, Roberto Santi.
United States Patent |
6,281,397 |
Santi , et al. |
August 28, 2001 |
Catalytic composition for the hydrogenation of olefinically
unsaturated organic compounds
Abstract
A catalytic composition effective in the selective hydrogenation
of olefinic double bonds, comprising the reaction product between:
(A) at least one complex of a transition metal having the following
general formula (I): wherein: M is selected from titanium and
zirconium, preferably titanium; each of the radicals R.sup.1,
R.sup.2, R.sup.3 or R.sup.4, independently, represents an organic
or inorganic group of an anionic nature .sigma.-bound to M, on the
condition that at least one, and preferablyat at least two, of
these radicals is an organic group; and (B) at least one
organometallic compound of magnesium having the following formula
(II): wherein: R.sup.5 or R.sup.6 each independently represent an
aliphatic or aromatic hydrocarbon group having from 1 to 20 carbon
atoms, and "n" is a decimal number between 0 and 2.0. Said
catalytic composition advantageously and selectively promotes the
direct hydrogenation of double bonds of an olefinic type, with high
rates and with a reduced formation of isomers.
Inventors: |
Santi; Roberto (Novara,
IT), Masi; Francesco (S. Angelo Lodigiano-Lodi,
IT), Longhini; Gianfranco (Vercelli, IT) |
Assignee: |
Enichem S.p.A. (Milan,
IT)
|
Family
ID: |
11378705 |
Appl.
No.: |
09/235,378 |
Filed: |
January 22, 1999 |
Foreign Application Priority Data
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Jan 27, 1998 [IT] |
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MI98A0137 |
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Current U.S.
Class: |
585/250; 585/266;
585/269; 585/271; 585/273; 585/275 |
Current CPC
Class: |
B01J
31/0212 (20130101); B01J 31/122 (20130101); C07B
35/02 (20130101); C07C 5/03 (20130101); C07C
67/303 (20130101); B01J 2231/645 (20130101); C07C
2531/12 (20130101); C07C 2531/22 (20130101) |
Current International
Class: |
B01J
31/12 (20060101); C07C 5/00 (20060101); C07B
35/00 (20060101); C07B 35/02 (20060101); C07C
67/303 (20060101); C07C 5/03 (20060101); C07C
67/00 (20060101); C07C 013/00 () |
Field of
Search: |
;585/250,266,269,271,273,275 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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137 329 |
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Aug 1979 |
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DE |
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0 298 408 |
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Jan 1989 |
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EP |
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Other References
Martin F. Sloan, et al., Journal Of The American Chemical Society,
vol. 85, pp. 4014-4018, "Soluble Catalysts for the Hydrogenation of
Olefins", Dec. 20, 1963..
|
Primary Examiner: Killos; Paul J.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier
& Neustadt, P.C.
Claims
What is claimed is:
1. A process for the selective hydrogenation of an olefinic double
bond of an olefinically unsaturated substrate, comprising:
contacting said substrate with hydrogen;
reacting said substrate with said hydrogen in the presence of a
catalytic composition comprising the reaction product between:
(A) at least one complex of a transition metal having formula
(I):
wherein
M is a metal selected from the group consisting of titanium and
zirconium;
each of the radicals R.sup.1, R.sup.2, R.sup.3 or R.sup.4
independently represents an anionic organic group .sigma.-bonded to
M or an anionic inorganic group .sigma.-bonded to M;
wherein at least one of said radicals R.sup.1, R.sup.2, R.sup.3 and
R.sup.4 is an organic group; and
(B) at least one organometallic magnesium compound of formula
(II):
wherein R.sup.5 or R.sup.6 each independently represent an
aliphatic or aromatic hydrocarbon group having from 1 to 20 carbon
atoms; and
wherein n is a decimal number between 0 and 2.0.
2. The process according to claim 1, wherein said substrate
comprises from 2 to 100 carbon atoms and consists of an aliphatic
olefin having from 2 to 100 carbon atoms, an aromatic olefin having
from 2 to 100 carbon atoms, an ester of an unsaturated carboxylic
acid with an aromatic alcohol, an ester of an unsaturated
carboxylic acid with an aliphatic alcohol, an ester of an
unsaturated carboxylic acid with a phenol, a vinyl ester of an
aliphatic acid, a vinyl ester of an aliphatic acid, a vinyl ester
of an aromatic acid or an organic imine.
3. The process according to claim 1, wherein said reacting with
said hydrogen is carried out under a hydrogen pressure of from 0.1
to 10 MPa;
wherein a temperature is of 0 to 150.degree. C.; and
wherein a molar ratio between metal M and said olefinic double bond
of said olefinically unsaturated substrate is up to 1:60,000.
4. The process according to claim 1, wherein at least two of said
radicals R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are an organic
group.
5. The process according to claim 1, wherein R.sup.6 and R.sup.5 in
said formula (II) are independently linear or branched aliphatic
hydrocarbon groups having from 2 to 10 carbon atoms.
6. The process according to claim 1, wherein n in said formula (II)
is equal to 2.
7. The process according to claim 1, wherein said complex of
formula (I) is dispersed in an inert liquid medium selected from
the group consisting of an aliphatic saturated hydrocarbon, a
cycloaliphatic saturated hydrocarbon and mixtures thereof.
8. The process according to claim 1, wherein said radicals R.sup.1,
R.sup.2, R.sup.3 and R.sup.4 in said formula (I) are the same;
and
wherein said radicals R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are
selected from the group consisting of a carboxylate, an amide, an
alcoholate and a .beta.-diketonate.
9. The process according to claim 1, wherein a molar ratio between
the magnesium compound of formula (II) and the compound of formula
(I) is between 1:1 and 20:1.
10. The process according to claim 1, wherein said metal M in said
formula (I) is titanium and a molar ratio between magnesium and
titanium is between 2:1 and 10:1.
11. The process according to claim to claim 1, wherein said
catalytic composition further comprises an additive (C).
12. The process according to claim 11, wherein said additive is a
polar aprotic organic compound having from 2 to 30 carbon
atoms.
13. The process according to claim 11, wherein said additive is an
aliphatic or aromatic ether; and
wherein a molar ratio between said metal M in said formula (I) and
said additive is between 0.1 and 100.
14. The process according to claim to claim 1, wherein in formula
(I) each R.sup.1, R.sup.2, R.sup.3 or R.sup.4, is independently
selected from the group consisting of a hydride, a halide, a
C.sub.1 -C.sub.8 alkyl group, a C.sub.3 -C.sub.15 alkylsilyl group,
a C.sub.5 -C.sub.8 cycloalkyl group, a C.sub.6 -C.sub.10 aryl
group, a C.sub.1 -C.sub.8 alkoxyl group, a C.sub.1 -C.sub.8
carboxyl group, a C.sub.2 -C.sub.10 dialkylamide group and a
C.sub.4 -C.sub.20 alkylsilylamide group.
Description
The present invention relates to a catalyst for the hydrogenation
of olefinically unsaturated compounds, comprising at least one
compound of titanium.
More specifically, the present invention relates to a process for
the selective hydrogenation of unsaturated compounds containing at
least one olefinic double bond, and a catalyst based on
non-cyclopentadienyl derivatives of titanium combined with a
suitable co-catalyst.
The hydrogenation of unsaturated substrates is a technology
widely-used for obtaining products which can be used in various
fields, from the food industry to the field of plastic materials
and the like. Several methods are known for the hydrogenation of
olefinic double bonds (chemically a reduction by means of
hydrogen), most of which use gaseous hydrogen in the presence of a
suitable catalyst. The latter normally comprises a transition
metal, usually a metal of group 10 of the periodic table, i.e. Ni,
Pd or Pt. If these are present as impurities in the hydrogenated
substrate, they can cause aging phenomena or toxicological problems
in the case of food.
Catalysts normally used comprise:
(1) supported heterogeneous catalysts consisting of inert materials
(for example silica, alumina, carbon) onto which a metal such as
nickel, platinum, palladium, etc. is deposited, and
(2) non-supported catalysts obtained by reacting an organometallic
compound of nickel, cobalt, titanium, etc., with a reducing
compound such as an organoaluminum or an organolithium.
With respect to supported heterogeneous catalysts (1),
non-supported catalysts (2) have the benefit of a greater activity.
This is a significant advantage as it allows blander hydrogenation
conditions to be used, with smaller quantities of catalyst.
EP-A-434.469 describes a catalytic composition which comprises (a)
at least one titanium bis-cyclopentadienyl derivative and (b) at
least one compound selected from those having general formula (i)
M.sup.1 (AlR.sup.1 R.sup.2 R.sup.3 R.sup.4) and (ii) M.sup.1
(MgR.sup.5 R.sup.6 R.sup.7), wherein M.sup.1, is selected from
lithium, sodium and potassium. Compound (i) can be obtained by the
reaction of an organic compound of an alkaline metal with an
organometallic derivative of aluminum, whereas compound (ii) can be
obtained by the reaction of an organo-alkaline compound with an
organo-magnesium derivative.
EP-A-601.953 describes a hydrogenation process carried out in the
presence of a catalyst having the general formula Cp.sub.2
Ti(Pho).sub.2 or Cp.sub.2 Ti(CH.sub.2 PPh.sub.2).sub.2, wherein Cp
is C.sub.5 H.sub.5.
The above catalysts based on titanium are characterized by the
presence of groups of the cyclopentadienyl type coordinated to the
metal atom. In accordance with this it is generally thought that
the active catalytic species consists of a stabilized titanium
complex having a reduced oxidation state. These catalysts however
have catalytic activities and a durability (average life of the
catalyst during the hydrogenation) which are still unsatisfactory
for normal industrial processes, in many cases requiring the use of
high quantities of metal with the consequent serious contamination
of the hydrogenated product. This particularly occurs when the
solvent in which the hydrogenation process is carried out is an
aliphatic hydrocarbon, such as cyclohexane or heptane, which, on
the other hand, is preferable as a solvent compared to aromatic
hydrocarbons owing to its greater volatility and lower
toxicity.
In addition, it has also been observed that, when the above
complexes of the metallocene type are used as hydrogenation
catalysts, a significant isomerization reaction of the unsaturated
hydrocarbons parallelly takes place, obtaining at times high
percentages of product different from that desired. This has the
double disadvantage of a decrease in the selectivity and greater
difficulty in separating the undesired products.
Compositions are also known which are based on non-metallocene
compounds of transition metals and alkyl derivatives of aluminum as
activators, which have a certain catalytic activity in
hydrogenation reactions. The publication Journal of the American
Chemical Society, Vol. 85 (1963), page 4014 onwards., describes in
particular catalytic compositions for the hydrogenation of
unsaturated aliphatic substrates, based on titanium alkoxides and
aluminum alkyls or lithium alkyls. The catalytic activity of these
compositions however is insufficient for convenient use on an
industrial scale. The same publication also mentions that the
substitution of the aluminum alkyl activator with equivalent
quantities of a Grignard reagent (butylmagnesium bromide) leads to
the total deactivation of the catalyst.
The Applicant has now surprisingly found that it is possible to
obtain a composition based on titanium or zirconium, which is
capable of catalyzing the selective hydrogenation of olefinic
double bonds and overcomes the above disadvantages, obtaining
significantly higher catalytic activities than those so far
registered in the known art for analogous systems. In addition,
this composition does not contain metals with a high toxicity such
as Cr, Pt, Ni, and can be used with fewer problems also in the food
industry.
In accordance with this, the present invention relates to a
catalytic composition effective in the selective hydrogenation of
olefinic double bonds, comprising the reaction product between:
(A) at least one complex of a transition metal having the following
general formula (I):
wherein: M is selected from titanium and zirconium, preferably
titanium;
each of the radicals R.sup.1, R.sup.2, R.sup.3 or R.sup.4,
independently, represents an organic or inorganic group of an
anionic nature .sigma.-bonded to M, and may, particularly, be
hydride, halide, a C.sub.1 -C.sub.10 alkyl group, a C.sub.2
-C.sub.15 alkylsilyl group, a C.sub.5 -C.sub.15 cycloalkyl group, a
C.sub.6 -C.sub.15 aryl group, a C.sub.1 -C.sub.15 alkoxyl group, a
C.sub.1 -C.sub.15 carboxyl group, a C.sub.2 -C.sub.15 dialkylamide
group and a C.sub.4 -C.sub.20 alkylsilylamide group; on the
condition that at least one, and preferably at least two, of these
radicals is an organic group; and
(B) at least one organometallic compound of magnesium having the
following formula (II):
wherein: R.sup.5 or R.sup.6 each independently represent an
aliphatic or aromatic hydrocarbon group having from 1 to 20 carbon
atoms, and
"n" is a decimal number between 0 and 2.0.
A second aspect of the present invention relates to a process for
the preparation of said catalyst, comprising, in particular,
putting the above compounds having formulae (I) and (II) in contact
and reacting with each other, preferably in the presence of a
liquid medium as diluent.
A further aspect of the present invention relates to a selective
hydrogenation process of the olefinic double bonds of an
olefinically unsaturated substrate, comprising putting said
substrate in contact and reacting with hydrogen under appropriate
conditions of pressure and temperature, in the presence of said
catalyst and, optionally, an inert diluent which is normally a
solvent of the substrate to be hydrogenated.
The compounds having formula (I) which form component (A) of the
catalytic composition of the present invention belong to known
groups of derivatives of titanium and zirconium and are normally in
the solid or liquid state at room temperature. The methods for the
preparation of many of these are described in specific literature
together with the physico-chemical properties. However the
compounds not described in literature can also be prepared
analogously to the known methods.
According to the present invention, each R radical (R=R.sup.1,
R.sup.2, R.sup.3 or R.sup.4) in formula (I) may independently be of
an organic or inorganic nature but must be bonded to the metal M
with a covalent (or also covalent-ionic) bond of the ".sigma."
type, having a cylindrical symmetry.
Bonds of the ".pi." type are therefore excluded, such as, for
example, the bond of a cyclopentadienyl group in a metallocene
derivative. In addition, in the compound having formula (I), at
least one R group of an organic nature must be present, i.e.
containing at least one carbon atombonded to a hydrogen atom. In a
preferred embodiment, at least two R groups are of an organic
nature and, more preferably, all four R groups are of an organic
nature.
Inorganic R groups are, for example, hydride, halides, particularly
chloride and bromide, nitrates and nitrites, --N.sub.3 azide,
--N.sub.2 H.sub.2 hydrazide, --NH.sub.2 amide, ---CO.sub.3 H
hydrogencarbonate, oxalate groups, etc.
R groups having formula (I) of an organic nature are, for example,
alkyls, aryls, alkylsilyls, carboxylates, amides, alcoholates,
thiols and .beta.-diketonates. Also included in the scope of the
present invention are compounds having formula (I) in which two R
groups (or also three of these groups, when this is compatible with
the steric characteristics of the compound) can be joined to each
other to form a cyclic structure comprising the metal M itself.
Preferred organic R groups are those selected from C.sub.1
-C.sub.10 alkyl, C.sub.2 -C.sub.15 alkylsilyl, C.sub.5 -C.sub.15
cycloalkyl, C.sub.6 -C.sub.15 aryl, C.sub.1 -C.sub.15 alkoxyl,
C.sub.1 -C.sub.15 carboxyl, C.sub.2 -C.sub.15 dialkylamide and
C.sub.4 -C.sub.20 alkylsilylamide groups. Particularly preferred
groups are aliphatic or cycloaliphatic, linear or branched,
alcoholate or carboxylate groups such as, for example, methoxide,
ethoxide, propoxide, isopropoxide, butoxide, trifluoromethoxide,
cyclohexyloxide, octyloxide, diethyleneglycoldioxide and similar
alkoxides, acetate, trifluoroacetate, butyrate, octanoate,
versatate, cyclohexanoate and similar carboxylates. Even more
preferred, for the purposes of the present invention are compounds
having formula (I) in which at least two R groups, even better all
R groups, are alcoholates.
Typical non-limiting examples of compounds having formula (I) which
can be used for the formation of the catalytic composition of the
present invention are listed hereunder:
Ti(OCH.sub.3).sub.4 Ti(OC.sub.2 H.sub.5).sub.4
Ti(OC.sub.4 H.sub.9).sub.4 TiO(acetylacetonate).sub.2
Ti(OCOC.sub.3).sub.4 Ti[OCON(.sup.i pr).sub.2 ].sub.4
Ti[N(CH.sub.3).sub.2 ].sub.4 Ti(C.sub.6 H.sub.5).sub.4
Ti(OC.sub.6 H.sub.5).sub.4 TiCl.sub.2 (.beta.-dinaphtholate)
According to the present invention, the above compounds having
formula (I) can be used in pure form, or supported on an inert
solid medium consisting, for example, of a porous inorganic solid,
such as silica, alumina, silicoaluminates, optionally dehydrated
and activated according to the methods known in the art, or
consisting of a polymeric organic solid such as polystyrene, so as
to obtain, at the end of the preparation, a supported catalytic
composition. In this case the compounds having formula (I) are
present in an adsorbed form on the surface of the organic or
inorganic solid, but they can also be more stably bound to the
solid by means of a covalent bond, as described in specific
literature.
The organo-magnesium derivatives having formula (II) are typically
selected from magnesium dialkyls. This group of compounds is
well-known to experts in the field and there are numerous methods
for their preparation. Many of these magnesium compounds are
commercial products, normally in the form of a solution in an inert
aliphatic hydrocarbon. Among organometallic compounds of magnesium
suitable for the preparation of the catalytic composition of the
present invention, magnesium dialkyls are preferred, wherein
R.sup.5 and R.sup.6 are independently selected from linear or
branched C.sub.1 -C.sub.16, preferably C.sub.1 -C.sub.10 alkyls.
Typical examples of magnesium dialkyls are magnesium di-n-butyl,
magnesium di-isobutyl, magnesium di-isopropyl, magnesium
butyl-isobutyl, magnesium di-cyclohexyl, magnesium butyl-octyl,
magnesium diaryl and relative mixtures.
With respect to the magnesium compound having formula (II), which
forms component (B) of the present catalytic composition, this is
added to the reaction environment preferably in the form of a
solution in an aliphatic or cycloaliphatic hydrocarbon solvent,
such as for example, cyclohexane.
The catalytic composition of the present invention is obtained by
means of a process in which the above components (A) and (B) are
put in contact with each other, under such conditions as to produce
a reaction. The molar ratio between the magnesium compound having
formula (II) and the compound of titanium or zirconium having
formula (I) is preferably between 1:1 and 20:1, more preferably
between 2:1 and 10:1. The reaction product obtained, which forms
the catalytic principle or one of its precursors, has not yet been
sufficiently characterized, and only indirectly, by its use in
hydrogenation catalysis.
Compound (I) in the formation of the catalytic composition of the
present invention can be introduced in pure form, or, preferably,
it can be dispersed in an inert liquid medium, either as a
suspension, if insoluble in said liquid, or as a homogeneous
solution when the liquid is a solvent of the compound having
formula (I).
The diluent can also be introduced into the reaction container
before charging both components (A) and (B). It must be inert
towards the compounds having formulae (I) and (II). The diluent is
preferably selected from aliphatic or cycloaliphatic saturated
hydrocarbons having from 3 to 15 carbon atoms and relative
mixtures. Typical examples of these diluents are propane, butane,
n-hexane, n-pentane, iso-pentane, n-heptane, octanes, decanes,
cyclopentane, variously alkylated cyclopentanes, cyclohexane,
variously alkylated cyclohexanes, "isopar" (mixture of paraffins).
The preferred diluent is cyclohexane.
Depending on the nature of groups R.sup.1, R.sup.2, R.sup.3 and
R.sup.4, the solubility of the compound having formula (I) in the
reaction diluent with the compound having formula (II) may vary
considerably. Organic groups such as alcoholates or carboxylates
increase the solubility of these complexes in aliphatic
hydrocarbons. It has been observed however that in certain cases,
at the end of the reaction of components (A) and (B), or, in any
case, after contact of the catalyst with hydrogen, the active
principle which is formed is of a solid nature, in the form of a
fine particulate in suspension in the inert diluent which also
forms the liquid medium in which the hydrogenation process
preferably takes place.
The preparation of the catalytic composition of the present
invention can optionally be carried out in the presence of an
additive (C) consisting of a polar aprotic organic compound,
preferably having from 2 to 30 carbon atoms, which has a
stabilizing function of the catalytic site, whereas effects on its
activity are not usually observed. Compounds of this type are also
known as Lewis bases, and comprise different groups of aliphatic or
aromatic organic compounds containing at least one heteroatom
selected from N, P, O, S, As and Se.
Preferred additives (C) are ethers, such as for example,
dimethylether, diethylether, di-n-propylether, diisopropylether,
di-n-butylether, di-sec-butylether, di-t-butylether, diphenylether,
methylethylether, ethylbutylether, butylvinylether, anisol,
ethylphenyl ether, ethyleneglycoldimethylether,
ethyleneglycoldiethylether, ethyleneglycol dibutylether,
diethyleneglycoldimethylether, diethyleneglycoldiethylether,
diethyleneglycoldibutylether, polyethyleneglycoldimethylethers,
polyethyleneglycoldiethylether, polyethyleneglycoldibutylether,
tetrahydrofuran, alpha-methoxytetrahydrofuran, ethers of
2-hydroxymethyltetrahydrofuran, pyrane, dioxane,
di(tetrahydrofuran)propane. Particularly preferred are cyclic
ethers, such as tetrahydrofuran or pyrane and di- or poly-ethers,
such as C.sub.1 -C.sub.20 ethers of ethylene glycol and
diethyleneglycol, even more preferred are C.sub.1 -C.sub.4 ethers
of glycol and ethylene diglycol.
The molar ratio M/(C) between the metal M and the additive (C),
when the latter is present, is preferably higher than 0.01. This
ratio is more preferably between 0.1 and 100; for ratio values
higher than 100, the possible advantageous effect of the
co-ordinating compound is no longer significant. Particularly
preferred ratios are between 1 and 20.0.
The modifier (C) can be added as such or, preferably, in an
aliphatic or cycloaliphatic hydrocarbon solution, more preferably
mixed with component (A). Alternatively, the modifier (C) can be
introduced into the reaction environment together with the compound
having formula (II), or separately, diluted in the solvent used for
the hydrogenation process.
According to a particular aspect of the present invention, the
above components (A), (B) and, optionally, (C), are put in contact
and reacted with each other in the presence of an aromatic
hydrocarbon, normally mixed with the reaction diluent. This
aromatic hydrocarbon is preferably present in such quantities as to
have a molar ratio with respect to the metal M of component (A)
ranging from 10 to 1000, and is selected from compounds having from
6 to 20 carbon atoms, such as, for example, toluene, xylenes,
ethylbenzene, 6-dodecylbenzene, naphthalene, tetraline, biphenyl,
indane and their mixtures.
Under the above conditions, at the end of the contact between the
reagents, a finely subdivided, dark-coloured, from brown to
purplish-brown, suspension is preferably formed. Depending on the
nature of the components and reactions conditions, a homogeneous
solution may initally be formed which subsequently becomes a
suspension.
As far as the temperature and reaction times between (A) and (B)
are concerned, these are not particularly critical and are within
wide limits, to obtain the catalyst of the present invention. It is
preferable however for the temperature to be between 0.degree. C.
and 100.degree. C., more preferably between 20.degree. C. and
70.degree. C. The contact time between the reagents, which in
practice is the activation time of the catalytic system, is
appropriately selected in relation to the temperature and other
reaction conditions (especially in relation to the possible
presence of hydrogen and the additive (C)), and ranges from a few
minutes to several hours, usually over 10 minutes and up to 20
hours, preferably from 1 to 10 hours.
The preparation of the catalyst must be carried out in an inert
atmosphere. The term "inert atmosphere" refers to an atmosphere of
gases which do not react with any of the species present in the
reaction environment. Typical examples of these gases are helium,
neon, argon, and relative mixtures. Alternatively hydrogen can also
be used. Air and oxygen are not appropriate because they oxidate or
decompose the hydrogenation catalyst making it inactive. Nitrogen
is also not appropriate as in certain cases it may react with the
activated form of the catalyst, causing undesired
modifications.
According to another embodiment of the present invention, the
catalytic composition in question can be prepared in the presence
of the unsaturated compound which is to be hydrogenated. The latter
can form the diluent itself in which the preparation of the
catalyst is effected, or it can be mixed with an inert diluent of
the type described above. In particular, the compound to be
hydrogenated can be added entirely or partially to component (A)
before the reaction with component (B). Alternatively, the
unsaturated compound is added after contact between (A) and (B),
but before introducing the hydrogen. In another variation of the
present invention, (A) and (B) are put in contact with each other
in an atmosphere of hydrogen and the substrate is subsequently
introduced.
The present invention also relates to a process for the selective
hydrogenation of olefinic double bonds in unsaturated organic
substrates, which comprises putting the substrate to be
hydrogenated in contact with hydrogen, preferably in a suitable
liquid medium, in the presence of the catalytic composition
described above, for a period sufficient to obtain the desired
hydrogenation degree. This is normally as high as possible and
generally exceeds 90%, preferably 97%, referring to the
disappearance of olefinic double bonds. The scope of the present
invention does not exclude however partial hydrogenation processes
of the substrate, in the presence of the catalytic composition in
question.
Among the various substrates which can be hydrogenated in
accordance with the process of the present invention, those whose
molecule comprises from 2 to 100 carbon atoms, preferably from 4 to
50 carbon atoms are preferred. More preferably, these substrates to
be hydrogenated have at least one primary olefinically unsaturated
bond, i.e. comprising the radical .dbd.CH.sub.2 or the radical
.ident.CH. Typical substrates which can be hydrogenated with the
process of the present invention are the usual aliphatic or
aromatic olefins having from 2 to 50, preferably from 4 to 25,
carbon atoms, such as, for example, 1-butene, isobutene, 1-octene,
cyclohexene, cyclohexadiene, undecene, cyclododecatetraene,
norbornene, styrene (selective hydrogenation to ethylbenzene),
divinylbenzenes, indene, conjugated dienes such as butadiene,
isoprene, chloroprene, non-conjugated dienes such as
ethylidenenorbornadiene, 1,4-hexadiene and the like, acetylene
derivatives such as acetylene, 2-butine, 1-hexine. Equally suitable
as substrates are also olefins and styrene derivatives comprising
heteroatoms such as, for example, halogens, especially chlorine and
fluorine, silicon, boron, sulfur, oxygen. Other unsaturatetd
substrates consist, for example, of esters of unsaturated fatty
acids, such as linoleic or ricinoleic acids, esters of unsaturated
acids with a short chain such as, for example, acrylic,
methacrylic, maleic or fumaric acid, vinyl esters of aliphatic or
aromatic acids, organic imines (also commonly called Schiff
bases).
The hydrogenation of these substrates can be carried out in an
inert diluent medium, or also on the compound to be hydrogenated as
such. The process can be carried out in suitable reactors, under
hydrogen pressure usually ranging from 0.1 to 10 MPa, at
temperatures ranging from 0 to 150.degree. C., preferably between
50 and 120.degree. C., and for times less than 5 hours, more
preferably between 30 minutes and 120 minutes, depending on the
substrate to be hydrogenated and the hydrogenation degree desired.
Blander conditions can be used, for example, if a primary double
bond is to be hydrogenated, leaving a secondary one intact in a
nonconjugated diene.
According to an embodiment, the solution of the substrate to be
hydrogenated is charged, under a hydrogen atmosphere, into the
hydrogenation reactor followed by the catalytic composition
dispersed in the diluent. The whole mixture is then pressurized
with hydrogen and brought to the desired temperature. When the
hydrogenation is complete, the hydrogenated product is recovered
according to the known techniques which comprise, for example,
distillation of the solvent, or distillation of the hydrogenated
substrate.
The catalytic compositions which can be obtained with the process
of the present invention are also active in the hydrogenation
process in very low quantities, indicatively up to 10 ppm of M with
respect to the substrate to be subjected to hydrogenation, with a
ratio between moles of metal M and olefinic double bonds of up to
1:60,000. This is a definite advantage with respect to the
catalysts of the known art. It should also be pointed out that the
hydrogenation process of the present invention allows the
hydrogenated product to be obtained without producing significant
quantities of isomerization product.
The present invention is further illustrated by the following
examples which however in no way restrict the overall scope of the
invention itself.
COMPARATIVE EXAMPLES 1-3 AND EXAMPLES 4-16
The general procedure adopted for carrying out the experiments
described in examples 1 to 16 is specified hereunder. Table 1 below
summarizes the data and the quantitative and qualitative results
relating to each example, together with any variations in the
general procedure.
PREPARATION OF THE CATALYTIC COMPOSITION
0.12 mmoles of the compound having formula (I) which forms
component (A), 20 ml of anhydrous cyclohexane, optionally the
activator (C) as an 0.45 M solution in anhydrous cyclohexane, and
0.72 ml of a 1 M solution of Mg(butyl).sub.2 in n-heptane, which
forms component (B), are charged, in an argon atmosphere, into a
tailed test-tube equipped with a magnetic stirrer. The mixture is
left under stirring for 2 hours at room temperature.
HYDROGENATION REACTION
The catalytic solution prepared as above is siphoned in a 100 ml
autoclave previously maintained under argon. The unsaturated
substrate to be hydrogenated, previously distilled and conserved on
molecular sieves, is then charged. The autoclave is pressurized
with 50 atm of hydrogen and brought to a temperature of 60.degree.
C. by heating with a bath. The hydrogenation is carried out under
these conditions for a duration of 90 minutes, continuously feeding
hydrogen to keep the pressure value constant.
At the end of the reaction, the autoclave is unloaded, operating in
an atmosphere of air, obtaining a spongy, dark-coloured suspension
which becomes pale yellow on contact with air. The suspended
particulate (catalyst residue) is separated by sedimentation and
the solution obtained is analyzed by gaschromatography and gas-mass
to determine the content of hydrogenated substrate and possible
isomers. The results are summarized in table 1 below.
TABLE 1 Hydrogenation of unsaturated substrates in cyclohexane
Component Additive Activation (moles Mg)/ Isomers Yield Example
Olefin (A) (C) time (h) (moles Ti) (%) (%) Notes 1(*) 1-octene
TiCl.sub.4 DME 20 6 4 37.5 -- 2(*) 1-octene TiCl.sub.4 DBG 20 6 6
48 -- 3(*) 1-octene TiCl.sub.4 DBG 2 6 1.5 15 activation at
70.degree. C. 4 1-octene Ti(O-Bu).sub.4 DBG 20 6 9.9 90 -- 5
1-octene Ti(O-Bu).sub.4 DBG 20 6 n.d. 100 activation in the
presence of 1-octene 6 1-octene Ti(O-Bu).sub.4 -- 2 6 n.d. 100 -- 7
1-octene Ti(O-Isopr).sub.4 DBG 2 6 n.d. 100 -- 8 1-octene
Ti(O-Bu).sub.4 DBG 2 6 n.d. 100 activation at reflux 9 1-octene
Ti(O-Bu).sub.4 DBG 2 6 n.d. 100 cyclohexane = 100 ml 10 1-octene
Ti(O-Bu).sub.4 DBG 2 6 <1 99 1-octene/Ti = 10,000 11 1-octene
Ti(O-Bu).sub.4 -- 2 1 11 58 -- 12 1-octene Ti(O-Bu).sub.4 -- 2 2
7.5 92 -- 13 1-octene Ti(O-Bu).sub.4 -- 2 3 n.d. 100 -- 14 1-octene
Ti(O-Bu).sub.4 -- 2 3 2.7 97.2 1-octene/Ti = 10,000 15 cyclooctene
Ti(O-Bu).sub.4 -- 2 3 <1 76 -- 16 isoprene Ti(O-Bu).sub.4 -- 2 6
n.d. 23.4 -- Conditions: Cyclohexane = 20 ml; olefin = 120 mmoli;
molar ratio olefin/Ti = 1000; component (B) = Dibutylmagnesium;
pressure = 5 MPa; temp. = 60.degree. C.; duration = 90 minutes;
atomic ratio Mg/Ti = 6; molar ratio Ti/(C) = 9 Abbreviations: (*) =
Comparative Example; DME = Dimethylether; DBG =
Diethylenglycoldibutylether; n.d. = not determined
* * * * *